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      <title>2、JDBC使用连接池 - 交互式测验</title>
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      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>2、JDBC使用连接池 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
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                      <p id="question-text"></p>
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                    <div id="hint-container" class="hint-container"></div>
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      <script>
        const quizData = [
  {
    "question": "根据文档，数据库连接池最核心的优势是什么？",
    "options": [
      "通过复用预创建的连接，显著减少连接创建和销毁的开销，从而提升性能和进行资源管理。",
      "简化了SQL查询语句的编写，降低了开发难度。",
      "为数据库提供了数据加密功能，增强了数据传输的安全性。",
      "自动对数据库进行备份，防止数据丢失。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "文档开篇就明确指出，数据库连接池通过预先创建连接并保存在池中供程序复用，极大地减少了连接创建和销毁的开销。其核心优势是性能提升和资源管理。",
    "source": "文档中「JDBC使用连接池」部分",
    "hint": "思考一下，与每次都新建和关闭连接相比，预先创建一组连接并重复使用能带来什么好处？"
  },
  {
    "question": "在众多连接池实现中，哪一个因其卓越的性能而成为 Spring Boot 的默认选择？",
    "options": [
      "Apache DBCP",
      "HikariCP",
      "C3P0",
      "BoneCP"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档中明确提到，HikariCP 是一个轻量级、高性能的数据库连接池，以高效、低延迟为特点，在高并发场景下表现出色，并因此成为 Spring Boot 默认的数据库连接池实现。",
    "source": "文档中「常见的连接池」-「3. HikariCP」部分",
    "hint": "文档在介绍一个特定的连接池时提到：“它的性能在所有连接池中是公认最好的。”"
  },
  {
    "question": "在C3P0连接池配置中，`checkoutTimeout` 参数的作用是什么？",
    "options": [
      "设置连接在池中的最大空闲时间，超过此时间连接将被关闭。",
      "定义一个连接的最大生存周期，到期后会被强制回收。",
      "当连接池满时，客户端获取新连接所愿意等待的最大时间，超时则抛出异常。",
      "设置后台线程检查连接有效性的时间间隔。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "`checkoutTimeout` 参数指定了当连接池中所有连接都在使用中时，一个新的连接请求最多等待的时间。如果在指定时间内没有连接被释放，请求就会失败并抛出异常，这是一种防止应用因等待连接而被无限期阻塞的保护机制。",
    "source": "文档中「理解连接池参数的意义」-「1. checkoutTimeout」部分",
    "hint": "这个参数与“获取连接”时的行为有关，特别是在连接池繁忙、没有可用连接的情况下。"
  },
  {
    "question": "启用 `testConnectionOnCheckout=true` 配置会对系统产生什么主要影响？",
    "options": [
      "显著加快获取连接的速度，因为它跳过了验证步骤。",
      "可能会轻微增加获取连接时的开销，但能有效避免应用获取到已失效的数据库连接。",
      "只在连接归还到池中时才进行测试，对获取连接的性能没有影响。",
      "它会自动增加连接池的大小以应对连接失败的情况。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "将 `testConnectionOnCheckout` 设置为 `true`，意味着每次从连接池获取连接时，都会执行一个简单的测试查询（如 `SELECT 1`）来验证连接的有效性。这确保了应用的可靠性，但也为每次获取连接的操作增加了一点额外的性能开销。",
    "source": "文档中「理解连接池参数的意义」-「4. testConnectionOnCheckout」部分",
    "hint": "这是一个在“可靠性”和“性能开销”之间进行权衡的参数。"
  },
  {
    "question": "文档中描述的“连接池泄漏 (Connection Leak)”指的是什么问题，推荐的解决方案是什么？",
    "options": [
      "指数据库服务器的物理内存泄漏；解决方案是重启数据库。",
      "指网络传输过程中连接信息被窃取；解决方案是使用SSL加密连接。",
      "指应用程序获取连接后未正确释放，导致连接被耗尽；解决方案是在 `finally` 块中确保关闭连接，并开启泄漏检测功能。",
      "指连接池创建的连接数超过了配置的最大值；解决方案是减小 `maxPoolSize` 的值。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "连接池泄漏是一个常见问题，指的是程序从连接池借用了连接但在使用完毕后没有归还。这会导致池中的可用连接越来越少，最终耗尽所有连接，使新的请求无法获取连接。文档建议的核心解决方案是保证代码逻辑严谨（使用try-finally结构）和利用连接池自带的泄漏检测功能。",
    "source": "文档中「JDBC连接池中的常见问题」-「1. 连接池泄漏」部分",
    "hint": "这个问题与连接的“借用”和“归还”过程有关。如果只借不还，会发生什么？"
  },
  {
    "question": "配置参数 `maxStatements` 的主要目的是什么？",
    "options": [
      "限制单个用户能够执行的SQL语句总数。",
      "控制连接池能够缓存的预编译SQL语句的最大数量，以提升性能。",
      "定义单个事务中可以包含的SQL语句的最大数量。",
      "设置连接池中允许同时存在的最大连接数。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "`maxStatements` 用于开启和设置预编译语句（PreparedStatement）的缓存。通过缓存预编译的SQL，可以避免数据库对相同的SQL语句进行重复的解析和编译，从而在执行大量重复SQL操作时显著提高性能。",
    "source": "文档中「理解连接池参数的意义」-「5. maxStatements」部分",
    "hint": "这个参数与“预编译SQL”的性能优化有关。"
  },
  {
    "question": "根据文档，`maxIdleTime` 和 `maxConnectionAge` 这两个参数有何不同？",
    "options": [
      "两者功能相同，只是命名不同。",
      "`maxIdleTime` 控制连接总的存活时间，而 `maxConnectionAge` 控制连接的空闲时间。",
      "`maxIdleTime` 控制连接的空闲存活时间，超时则关闭；而 `maxConnectionAge` 控制连接的总生存周期，到期后无论是否空闲都会被关闭和替换。",
      "`maxIdleTime` 用于高性能场景，`maxConnectionAge` 用于高可用场景。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "这两个参数都用于管理连接的生命周期，但作用点不同。`maxIdleTime` 关注的是“空闲”状态，用于回收长时间不被使用的连接以节约资源。而 `maxConnectionAge` 关注的是连接的“年龄”，用于定期替换老旧连接，防止因长时间运行可能导致的连接不稳定或内存泄漏等问题，无论它是否一直处于繁忙状态。",
    "source": "文档中「JDBC连接池的性能优化」-「2. 连接的生命周期管理」部分",
    "hint": "一个参数关注连接的“空闲”时长，另一个关注连接从创建到现在的“总时长”。"
  }
];
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        let score = 0;
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            document.getElementById('quiz-footer').style.display = 'none';

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            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

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                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  